1. Field of the Invention
The invention relates to apparatus for crushing and shredding of solid waste material. More specifically it relates to apparatus in which two stacks of cutting and shredding elements are arranged on two substantially parallel shafts with spacers positioned between each pair of adjacent cutters on each shaft. Still more specifically it relates to such apparatus in which said spacers have cutting elements on their peripheries and serve also as cutters as well as spacers thereby increasing the efficiency of the comminuting apparatus. Still more specifically it relates to comminuting apparatus which has cutting edges from the bottom to the top, or from one end to the other end of the comminuting elements without any intermediate elements having no cutting edges whereby strings or wires in the waste material might be wound without meeting cutting edges.
2. State of the Prior Art
Various types of solid waste material have been the object for comminution in various types of apparatus. The comminuted material may be used for various purposes or used as land fill.
Recently there has been interest in comminuting discarded tires. Huge piles of tires have accumulated in various areas which present fire hazards. Once a pile of tires catches fire, either accidentally or intentionally to dispose of the tires, the burning is difficult to extinguish and the combustion fumes or products are very damaging to the environment.
To dispose of these discarded tires attempts have been made to use them in land fill. One practice is to deposit garbage and solid waste to a depth of 5 feet or more and then a layer of comminuted tires is imposed. Over this layer of comminuted tires there needs to be placed a layer of dirt to a depth of 4 inches or more.
In the comminution of tires the nylon cord or steel wire reinforcement used in most tires has a tendency to wrap around any rotating elements that may be in the comminuting apparatus. Therefore apparatus of increased efficiency for cutting these cords or wires is desired. Moreover heavy truck tires have a steel bead sometimes 0.5 in diameter running on the inside rim of the tires which presents a drastic challenge to the comminuting capability of the apparatus.
The interest in devices for comminuting waste material is evidenced by the number of patents granted for this purpose, for example, U.S. Pat. Nos. 1,477,502; 3,151,645; 3,529,782; 3,664,592; 3,695,520; 3,738,582 and 4,046,324.
U.S. Pat. No. 4,046,324 describes two vertically arranged shafts. The cutters in each column are separated from each other by spacers which have a smaller diameter than the diameter of the cutters and which provide enough space between two adjacent cutters to allow a cutter from the other stack to enter a portion of the space between the cutters on the first stack.
U.S. Pat. No. 85,067 shows apparatus for cutting straw involving a number of circular saw blades designed to cut the straw or similar fiber material. The saw blades are spaced from each other by spacers and have different diameters. A large diameter saw blade on one shaft is meshed between two blades of smaller diameter on the other shaft. Between each two large diameter saw blades there are two small diameter saw blades and each is separated from adjacent saw blades by spacers.
U.S. Pat. No. 219,170 describes circular saw blades used to disintegrate paper stock with blades of large diameter on one shaft and blades of smaller diameter on a second shaft. There is no indication of the blades meshing and the blades are separated from adjacent blades by washers or spacers.
In applicant's parent U.S. patent application Ser. No. 07/432,198, the following references were cited:
U.S. Pat. Nos. 4,046,324; 4,165,043; 4,709,197; 4,609,155; West German Pat. No. 2,831,953; Japanese Pat. No. 52,269; British Pat. No. 2,026,342 and Danish Pat. No. 18,722.
None of the prior art references show cutting edges throughout the height or length of the comminuting element. Therefore it is possible for waste material of a stringy type to become wrapped around the spacers. In some cases the build-up of wrapped stringy material has been reported to push apart the stacks of cutting elements.
The above-cited devices are shown capable of performance on easily comminuted materials, such as straw, sewage, etc. None of these have been shown capable of comminuting tires which are difficult to comminute and which have nylon or steel wire reinforcement therein and particularly huge truck tires which have a steel bead of about 0.5 inch diameter running along the inside rim of the tires.
The disposal of tires has become a major problem in most areas of the United States. It is estimated that approximately 250 million tires are discarded each year. These present environmental and ecological problems. Each tire gives an average of approximately 1.5 gallons of oil and 6 cubic feet of combustible gas. The amount of combustible materials therein present the danger of catching fire and difficulty in subduing the fires. In addition to the combustible nature of the material, piles of tires are often so high and of such considerable area that it is difficult to attack the fire in such piles. Attempts have been made to use tires without comminution in land fill. When the tires are used as such with trash and garbage, the tires eventually work their way to the surface. It is found necessary therefore to comminute the tires before using in land fill.
A number of states have passed legislation regulating the disposal of tires. For example, Florida, where approximately 17 million tires accumulate per year, has legislated that a disposal fee of one dollar per tire is to be paid upon the purchase of new tires. Eighty percent of the funds thus collected goes back to the respective counties for the purchase and maintenance of tire shredding equipment. These shredders, generally of the hammermill type cost approximately $175,000 or more each. This state regulates that shredded tires having no pieces of more than 2 inches in its greatest dimension may be used as land fill.
In the general practice of land fill, garbage must be covered at the end of each day with a layer of at least 6 inches of dirt and then treated with a stabilizer or hardening material so that by the next day the dumping trucks will be supported on this surface. However when a covering of two inches of comminuted rubber and four inches of dirt is used, the surface layer is sufficiently stabilized to support the trucks. This state also has anti-littering law which punishes a person found throwing away tires of 45 pounds or more by a fine and possible confiscation of the person's vehicle. With more states growing more conscious of the necessity of regulating tire disposal, the development of more efficient equipment and processes for the comminution of tires becomes a very important factor.